The present invention relates to a sheet end detecting mechanism which is disposed in a sheet conveyance path of a printer.
A printer which prints a full color image on a sheet of designated-type of paper, for instance, requires such a performance as printing of the image fully from one end to the other end of the sheet, which accordingly requires a sheet detecting sensor that accurately detects a front end of or a rear end of the sheet.
The printer usually utilizes a mechanical sheet detecting sensor which is displaced by passing of the recording sheet and an optical sheet detecting sensor which is sensitive to the reflected light from the recording sheet surface; the mechanical sheet detecting sensor, however, wherein a tip of a detecting lever is bent in an obtuse angle for prevention of being caught when the recording sheet is fed reversely, is inconvenient with a low sheet detecting sensitivity, such as errors of .+-.several millimeters, whereas the optical sheet detecting sensor has a problem of imperfect sheet end detection of such a sheet as is framed, and thus neither is fully adequate to printing without margins.